1. Field of the Invention
The invention relates to a wheel rim with a wheel disk made from a fiber composite material and with fasteners to fasten the wheel disk to a wheel hub of a vehicle, wherein the wheel disk has at least one opening to accommodate the wheel hub and the opening is formed with a conical centring surface for the seat of a fastener.
2. Discussion of Background Information
Wheel disks made from a fiber composite material are known for example from published document DE 1939910 A. The published document discloses a method for manufacturing wheels from fiber-reinforced plastics for motor vehicles in which, in an area of high tensions of the wheel disk or wheelbrace, reinforcing fibers are arranged in accordance with the direction of flow of the arising tensions, in a circle and radial to the axle. To increase the strength, additional fiber inserts are arranged on top of one another in this area. Neither the opening for the wheel hub, nor the seat of the wheel hub, nor a fastener, are described in any more detail. From the figures, a convex border area of the opening is visible, with the wheel disk terminating with a border surface that leads in the direction of the axle. In accordance with this, it is to be expected that the fiber layers located in the border area of the opening, that is to say in the area of the highest tensions, are, as a result of the loads introduced there, primarily under bending-related stress, which involves a considerable weakening of the fiber composite structure in this area and can form a starting point for delamination of the fiber layers.
From published document DE 101 45 630 A1 a wheel disk or wheel spider made from fiber composite material is known, wherein the fibers in the wheel spider are largely arranged in a radial direction. In addition, the wheel spider may contain webbing or fabric made from endless fiber strands oriented in a radial or circumferential direction. In the center of the wheel spider, the wheel spider may be firmly attached to an integrated wheel hub. The design of the opening for accommodating the wheel hub is not described in any more detail. From the drawing, a flat border area of the opening is visible, with the wheel disk terminating with a border surface that leads in a direction perpendicular to the axle, which serves as a seat for the cylindrical stub of the wheel hub. A bearing surface of the wheel hub indicates that the connection with the wheel disk is performed by means of a fastener through bracing against the flat border area of the opening of the wheel disk. Through the preload forces generated in this way, the fibers of the webbing or fabric of the wheel disk are pressed together, as a result of which the fiber composite structure is weakened considerably in this area.
From published document DE 689 22 982 T2 a vehicle wheel made from fiber-reinforced composite material is known which comprises a wheel rim with a wheel disk. For fastening the wheel disk to a wheel hub, the wheel disk has a central fastening opening to accommodate the wheel hub and a number of fastening openings arranged concentrically around the axle, which accommodate the connection elements, equipped with screw threads, to fasten the wheel disk to the wheel hub. The stud bolts are screwed on in an axial direction. To ensure an exact fit of the connection elements (stud bolts), each fastening opening is provided with a conical seat surface in the manner of a chamfer that has been cut in. The reinforcing fibers of the wheel disk are preferably arranged in planes perpendicular to the axle and end in the fastening openings i.e. the course of the fibers is interrupted here.
Disadvantageous is that through the design of the fastening openings, the wall cross-section of the wheel disk is tapered and hence the fiber composite structure of the wheel disk is weakened in the very area—the connection to the wheel hub of the vehicle—placed under high stress.
Furthermore, during the introduction of the preload forces into the wheel disk, the fiber layers are pressed together, as a result of which the fiber composite structure is likewise weakened.
A device of the generic kind is known from published document DE 196 08 601 A1. Here, a wheel rim with a wheel disk made from fiber-reinforced plastic is described in which the wheel disk has a central opening and is connected by means of a central fastening to the wheel hub or a fastening element of the wheel hub of the wheel hub. The fastening element is connected to the axle by means of several stud bolts. The central opening of the wheel disk has a conical centring surface in the direction of the fastening element to center the wheel disk on the fastening element. The central opening also has a conical centring surface in the direction of the central nut, in order to ensure the centric seat of the central nut and the clamping ring in between.
Although the conical centring surfaces provide an enlarged area for the introduction of the clamping forces, the design also results in the wall thickness of the wheel disk being reduced in the very area that is subject to high stresses and hence the strength of the fiber composite material being weakened.
Furthermore, this fastening solution requires a high level of effort in terms of production and assembly.
The problem underlying the invention is to provide a wheel rim which overcomes the aforementioned disadvantages of the prior art; in particular, the problem consists of improving the durability of the wheel connection and at the same time minimizing the production and assembly effort required.